Laser based photoepilation has been the object of study since the advent of the laser. It has been know for several years that optical pulses of the appropriate wavelength, pulse duration, and energy density impinging upon human skin will result in significant and enduring hair loss. The accepted theory for this phenomenon is that the penetration of the laser into the skin and its subsequent scattering results in heating of the hair shafts and follicles through selective absorption by melanin. The absorption of the radiation leads to heating of the follicle and subsequent thermal necrosis.
It has been found that for effective photoepilation to occur the energy must be penetrate approximately 3 mm into the tissue. Prevailing thought indicates that this means the absorption should occur in the melanin and not the oxyhemoglobin, thereby heating the regions around the hair follicle instead of heating the blood and blood vessels. Energy absorption in the melanin leads to elimination of the hair and the reduction or elimination of the ability of follicle to produce hair. Based on the absorption spectrum of melanin and oxyhemoglobin the wavelengths in the neighborhood of 700 nm have been thought to be efficacious. Therefore the Ruby laser at 694 nm, the Alexandrite laser around 760 nm, and flashlamps with emission spectrum centered near 700 nm have been used for this application. The aforementioned lasers are very inefficient, requiring high voltages, large supplies of cooling water. In addition, delivery of the energy to the skin surface is problematic due to the energy required for photoepilation. The pulse energies often exceed damage thresholds of delivery systems or are difficult channel to from the laser to the skin. The flashlamps themselves are inefficient, emit in all directions making efficient energy delivery difficult, and the flashlamps can be cumbersome to use in a handheld device. The convenient and controlled delivery of the optical energy of the appropriate wavelength, fluence and pulse duration to the skin surface for photoepilation in an efficient device has been difficult.